Middle distillate fuel containing additive combination to increase low temperature flowability

ABSTRACT

The low temperature flowability of a middle distillate petroleum fuel oil boiling within the range of about 250* to about 700* F. at atmospheric pressure is improved by adding to the fuel oil from about 0.1 to about 3 percent of an essentially saturated hydrocarbon fraction which is substantially free of normal paraffinic hydrocarbons and which has a number average molecular weight in the range of about 600 to about 3,000. The fuel oil also contains a polymeric additive, usually in a lesser amount than said high molecular weight paraffinic fraction, said polymeric additive being characterized by having an average of at least one long alkyl side chain for every four carbon atoms along the polymer chain. This additive combination is unique in that the polymeric additive does not interfere with the flow improving properties of the high molecular weight hydrocarbon, and the high molecular weight hydrocarbon does not interfere with the pour point depressing properties of the polymeric additive, whereas such interference is encountered when using other conventional polymeric pour depressants such as a copolymer of ethylene and an unsaturated ester.

United States Patent Feldman [75] Inventor: Nicholas Feldman,Woodbridge,

[73] Assignee: Esso Research and Engineering Company, Linden, NJ.

[22] Filed: Mar. 17, 1969 [21] Appl. No.: 807,965

[52] US. Cl. 44/62, 44/70 [51] Int. Cl C101 1/18 [58] Field of Search44/62, 70; 208/33, 208/15; 252/56 [56] References Cited UNITED STATESPATENTS 2,906,688 9/1959 Farmer et al. 208/45 2,177,732 10/1939 MacLaren44/80 2,917,375 12/1959 Hudson 44/62 2,664,388 12/1953 Winterhalter.....208/15 X 2,906,688 9/1959 Farmer et al. 203/33 3,069,245 12/ 1962 Wytheet al. 44/62 3,132,083 5/1964 Kirk 208/45 3,413,103 11/1968 Young et al.44/70 3,507,776 4/1970 l-lann 208/ 15 FOREIGN PATENTS OR APPLICATIONS1,223,976 9/1966 Germany 44/70 [1 1 3,773,478 Nov. 20, 1973 PrimaryExaminer-Daniel E. Wyman Assistant Examiner-Mrs Y. H. SmithAttorney-Pearlman & Stahl and Byron O. Dimmick [57 ABSTRACT The lowtemperature flowability of a middle distillate petroleum fuel oilboiling within the range of about 250 to about 700 F. at atmosphericpressure is improved by adding to the fuel oil from about 0.1 to about 3percent of an essentially saturated hydrocarbon fraction which issubstantially free of normal paraffinic hydrocarbons and which has anumber average molecular weight in the range of about 600 to about3,000. The fuel oil also contains a polymeric additive, usually in alesser amount than said high molecular weight paraffinic fraction, saidpolymeric additive being characterized by having an average of at leastone long alkyl side chain for every four carbon atoms along the polymerchain. This additive combination is unique in that the polymericadditive does not interfere with the flow improving properties of thehigh molecular weight hydrocarbon, and the high molecular weighthydrocarbon does not interfere with the pour point depressing propertiesof the polymeric additive, whereas such interference is encountered whenusing other conventional polymeric pour depressants such as a copolymerof ethylene and an unsaturated ester.

5 Claims, No Drawings MIDDEEQD STILL TE FUEL CONTAINING ADDITlVECOMBlNAT-IONTO I cREAsE LOW TEMPERATURE rLowABILITY :I'FI'ELD OF-TIIE- IVENTION l-leating' oi'ls' andi other middle distillate petroleum fuels,e.g. "Diesel fuels,- contain normal paraffin hydrocarbonfwaxes whichgjatlowtmperatures; tend to pre- 'cipitateinlargecrystalsin such a way-astoset up a gel structure which causes; merulro-1ose 'its fluidity. The

lowest temperatureat-"whioh' the fuel will 'still flow is generallyknowrr as 'the pour point. When the fuel temperaturereaches"orgoeslbelow the pour'point and the fuel is' "no longer "freelyflowable,difficillty arises in of the cry's'ta'ls 'that precipitate'fromthe fuel oil,thereby "reducing the te'riden'cy'ofthe'wax crystals to setinto a gellSrnall s'i'ze crystals aredesirable so that the precipitated'wax'will not clog the fine mesh screens that are providediri fueltransportation, storage, and dispensing equipment: lt-is' thus desirableto obtain notonly fuel "oils'w'ith lowpourpdints but also oils that'willform small wax crystals sothat' the clogging of filters'will not impairthe flow of the fuel atlow' operating tempera- 'tu'res.

- RELATEDART *It is taught in the application of Nicholas Feldman andWladim'ir Philippo'ffentitled Increasing Low Temperature FlowabilitybfMiddle Distillate Fuel,

SerQ'No; 807,95 3 filed simultaneously'with the present application andsubsequently'issued onMay 2, 1972 as U.S. Pat. No. 3,660,058, that aparaffinic hydrocarbon fraction that is substantially free of normalparaffin hydrocarbons ie, contains no more than about 5 "wt.

and'preferably nomore than about 1 wt. of normal paraffin hydrocarbons,and thathas a number average molecular weight of fr0m'about600 to about3,000, "when added to a middle distillate petroleum fuel oil in aconcentration of about 0.01 to about 3'wt. will depress the pour pointof the fuel oil to some extent and will also improve the low temperatureflowability of the saidpe'troleum fuel oil.

DESCRIPTION oF THE INVENTION In accordance with-the present invention,it has now beenfound' that further"improvement in the low tem- Iperature properties of a petroleum fuel oil can be obtained'if there'isemployed in combination with the highmolecularwei'ght hydrocarbonfraction a particular' type of polymeric pour 'point depressant which ischaracterized by having, on the average, at least one longdependentalkylhydrocarbon group for every 4 carbon atoms of the backbone of thepolymer. This combination of the hydrocarbon fraction and the polymerisuniquein that if 'theaforesaid hydrocarbon fractionis employed *in'conjunction'with most of the conventional polymeric'pour pointdepressant additives,

particularly those of the ester type or those comprising copolymers ofethylene and unsaturated esters, the improvement that would be obtainedin filterability by the use of the hydrocarbon fraction alone, as wellas the pour point depression that would be obtained by the polymericadditive alone, are often adversely affected. In some instances, whilethe filterability improvement contributed by the aforesaid hydrocarbonfraction is not adversely'affected, and in some cases is even im- 7proved, the pour point depressing action of the polymeric additive isimpaired. However, with the additive combination of thepresent'invention, neither the improved filterability nor the pour pointdepressing action is adversely affected.

More specifically, there are added to a waxy middle distillate petroleumfuel from about 0.1 to about 3 weight preferably from about 0.2 to 1 wt.of said high molecular weight, substantiallynormal-paraffinhydrocarbon-free hydrocarbon fraction, and from about0.005 to about 1 weight preferably from about 0.01 to 0.1 weight of thepolymeric'pour point depressant. The weight ratio of the two types ofadditive can vary from 50 parts of the added hydrocarbon fraction perpart of polymeric pour point depressant to about equal parts of the twotypes of additive. Preferably, about 5 to about 30 parts of the addednormalparaffin-free hydrocarbon fraction will be used per part ofpolymeric pour point depressant.

The-distillate fuel oils that can be improved by this invention includethose having boiling ranges within the limits of about 250 F. to about700 F. The distillate fuel oil can comprise straight run or virgin gasoil,

I cracked gas oil or a blend in any proportion of straight run andthermally and/or catalytically cracked distillates.

The most common petroleum middle distillate fuels are kerosine, dieselfuels, jet fuels and heating oils. Since jet fuels are normally refinedto very low pour points there will be generally no need to apply thepresent invention to such fuels. The low temperature flow problem ismost usually encountered with diesel fuels and with heating oils. Arepresentative heating oil specification calls for a 10 percentdistillation point no higher than about 440 F., a 50 percent point nohigher than about 520 F., and a percent point of at least 540 F. and nohigher than about 640 F. to 650 F., although some specifications set the90 percent point as high as 675 F. Heating oils are preferably made of ablend of virgin distillate, e.g. gas oil, naphtha, etc., and crackeddistillates, e.g. catalytic cycle stock. A representative specificationfor a diesel fuel includes a minimum flash point of F. and a 90 percentdistillation point between 540 F. and 640 F. (See ASTM DesignationsD-396 and D975) The pour point depressant used in this invention is apolymer or copolymer wherein the monomer relationship is'represented bythe formula:

wherein x is an integer 0 to 3, B is an alpha, beta unsaturated ester offrom 4 to 8 total carbon atoms, and A is an unsaturated compound of thegeneralized formula:

wherein R and R are hydrogen or methyl, R is a C to C alkyl groupconnected to the designated unsaturated carbon atom through an aromatichydrocarbon group or through an ester group, and R is either hydrogen, acarboxyl group, or the same as R When R is hydrogen or a carboxyl group,x does not exceed 2.

The polymer and copolymer pour point depressants used in this inventionwill have number average molecular weights within the range of about 800to 50,000, preferably about 1,000 to 10,000. Molecular weights can bedetermined by cryoscopic methods or by vapor phase osmometry.

A polymer of a monomer arrangement as depicted above, wherein x is zero,and wherein in monomer A, R and R are alkyl groups connected to theunsaturated carbon atoms through aromatic hydrocarbon groups isexemplified by an alkylated polystyrene or an acylated polystyrene, asmore fully described below.

Examples of monomer A wherein R is hydrogen or a carboxyl group and R islinked to the unsaturated carbon through an ester group include vinyllaurate, vinyl palmitate, C Oxo alcohol acrylate, C Oxo alcoholmethacrylate, allyl stearate, palmityl alcohol ester of alpha methylacrylic acid, mono C Oxo alcohol ester of fumaric acid, etc.

Examples of monomer A where R is the same as R and both are linked tothe unsaturated carbons through ester groups include didecyl maleate,di- C Oxo alcohol fumarate, di- C linear Oxo alcohol maleate (see U.S.Pat. No. 3,417,021), etc.

Examples of monomer B include vinyl acetate, dimethyl fumarate,isopropyl acrylate, ethyl methacrylate, di-isopropyl maleate, allylacetate, vinyl butyrate, etc.

The Oxo alcohols used in preparing the esters mentioned above areisomeric mixtures of branched chain aliphatic primary alcohols preparedfrom olefins, such as polymers and copolymers of C to C monoolefins,reacted with carbon monoxide and hydrogen in the presence of acobalt-containing catalyst such as cobalt carbonyl, at temperatures ofabout 300 to 400 F., under pressures of about 1,000 to 3,000 psi., toform aldehydes. The resulting aldehyde product is then hydrogenated toform the x0 alcohol, the latter being recovered by distillation from thehydrogenated prod- UCt.

Examples of specific copolymers useful in this invention include acopolymer of one mole of di-lauryl fumarate and two moles of isopropylmethacrylate, a copolymer of one mole of stearyl acrylate and 2.5 molesof vinyl butyrate, and a copolymer of one mole of vinyl palmitate and1.8 moles of vinyl acetate.

Particularly useful polymeric pour point depressants for'use in thisinvention comprise'alkylated polystyrenes, acylated polystyrenes andmixtures thereof. Especially preferred are alkylated polystyrenesprepared from essentially straight chain olefins having from about tocarbonat atoms, e. g. decene-l hexadecene-l, octadecene-l, eicosylene,and cracked paraffin wax, as well as acylated polystyrenes prepared fromaliphatic acylating agents, e.g. acid halides, of 8 to 20 carbon atomsin a straight chain, e.g. stearoyl chloride or lauroyl chloride.

Alkylation of polystyrene can be conducted by the process described inU.S. Pat. No. 2,756,265 of William C. Hollyday, Jr.

Typically, the process comprises the steps of dissolving polystyrene inan inert solvent such as monochlorobenzene, and heating the mixtureuntil the polystyrene is completely in solution. The mixture is thencooled to the selected reaction temperature (usually in the range ofabout 80 to 150 F.) at which time nitrobenzene and a Friedel-Craftscatalyst are added. The alkylating agent is then added dropwise and thereaction temperature is maintained by cooling or heating as necessary.After the completion of the reaction, the alkylates are purified by wellknown techniques.

Acylated polystyrenes are prepared by reaction of polystyrene with anacid chloride. See U.S. Pat. No. 3,069,245 of S. L. Wythe and W. C.Hollyday, Jr.

Typically, the method of acylation comprises dissolving the polystyrenein a suitable solvent, such as chlorobenzene, o-dichlorobenzene, ortetrachloroethylene and adding to the solution an equimolar quantity ofcarboxylic acid chloride/aluminum chloride complex at temperatures of 30to C. (preferably 40 to 60 C.), with provision for carrying away theevolved hydrogen chloride. After all the acid chloride/aluminum chloridecomplex has been added (one mole per mole of phenyl groups in thepolystyrene, plus a slight excess) and hydrogen chloride evolution hasstopped, the catalyst is destroyed with water or alcohol, the acylate istaken up in a suitable solvent, such as heptane or kerosene and washedwith water and alkaline solutions. The resinous product may be isolatedas the pure material by evaporating all solvents, or it may be used insolution for making blends in middle distillates.

The fractions of essentially saturated hydrocarbons that are used inaccordance with the present invention in conjunction with the polymericpour point depressants are generally amorphous solid materials havingmelting points within the range of about to 140 F. and having numberaverage molecular weights within the range of about 600 to about 3,000.This molecular weight range is above the highest molecular weight of anyhydrocarbons that are naturally present in the fuel oil.

An amorphous hydrocarbon fraction that is useful as a fuel oil flowimprover in accordance with this invention can be obtained bydeasphalting a residual petroleum fraction then adding a solvent such aspropane to the deasphalted residuum, lowering the temperature of thesolvent-diluted residuum and recovering the desired solid or semi-solidamorphous material by precipitation at low temperatures, followed byfiltration. The residual oil fractions from which the desired amorphoushydrocarbons are obtained will have viscosities of at least SUS at 210F. Most of these residual oils are commonly referred to as brightstocks.

In some instances products obtained by this procedure will be naturallylow in normal paraffin hydrocarbons and can be used in the presentinvention without further treatment. For example, by low temperaturepropane treatment of a deasphalted residual oil from certain Texascoastal crudes a precipitated high molecular weight amorphous fractioncan be obtained which has only a trace of normal paraffins, about 5percent of isoparaffins, about 73 percent of cycloparaffins and about 22percent of aromatic hydrocarbons. In other instances it is necessary totreat the high molecular weight fraction in some manner to reduce itscontent of normal paraffins. Removel of normal paraffins from anamorphous hydrocarbon mixture can be effected by complexing with urea,as will be illustrated hereinafter in one of the examples. Solventextraction procedures can also be used, but in many instances they arenot as effective as complexing techniques. Thus the amorphoushydrocarbon mixture can be dissolved in heptane or preferablya ketonesuch as methyl ethyl ketone atits boiling point and then when thesolution is cooled to room temperature the normal paraffms will bepredominantly precipitated and the resultant supernatant solution willgive a mixture containing soem normal paratfinsbut predominating incycloparaffins and isoparaffins.

Vacuum distillation can also be used for the removal of normalparaffinhydrocarbons from a high molecular weight paraffinic fraction,but such a procedure requires a very high vacuum, i.e. less than 5 mmHg, absolute pressure, preferably a pressure below 3 mm Hg, absolute,e.g. 2 mm or 120 microns. If the pressure used is 5 mm or higher, thenecessary temperature for the distillation is high enough to causecracking of the constituents, which is undesirable.

The combinations of flow improving additives and pour point depressantsherein described may constitute the sole additives that are incorporatedin the fuel oil compositions, or they can be employed in conjunctionwith other additives commonly used in distillate fuels, including rustinhibitors, antioxidants, sludge dispersants, demulsifying agents, dyes,haze suppressors, etc.

The nature of this invention and the manner in which it can be practicedwill be more fully understood when reference is made to the followingexamples, which include a preferred embodiment.

EXAMPLE 1 Fuel oil blends, were prepared using either of two middledistillate fuel oils consisting of mixtures of cracked distillates andheavy virgin naphtha. These middle distillate fuel oils are furthercharacterized as follows: (Percentages are by volume) Oils Tested:

Oil A: 80% cracked oil, FBP 630 F.

% heavy virgin naphtha Cloud Point +6 F. Pour Point -5 F.

Oil B: 85% cracked oil, FBP 660 F.

15% heavy virgin naphtha Cloud Point +l2 F.

Pour Point 5 F.

Comparative blends were prepared using each of the fuel oils to whichhad been added either a copolymer of vinyl acetate and ethylene; aterpolymer of ethylene, vinyl acetate, and an alpha olefin; an alkylatedpolystyrene; a copolymer of fumarate esters and vinyl acetate; a solidhydrocarbon fraction more fully described below; or combinations of thissolid hydrocarbon fraction with each of the separate polymeric pourdepressants mentioned above. Each blend was prepared by simple mixing ofthe additives with the respective fuel oil, using heat if necessary.Some of the additives were in the form of concentrates, e.g. a 45 wt.solution in kerosine; however, in the tabulated data the concentrationsgiven are of each actual ingredient. The ASTM pour points of thesevarious blends were measured and each of the blends was subjected to alow temperature filterability test which is run as follows:

A 200 milliliter sample of the oil is cooled at a controlled rate of 4F. per hour until a temperature of 0 F. is reached, this being thetemperature at which the flow test is conducted. The oil is thenfiltered through a US. 40 mesh screen at the test temperature, and thevolume percentage of oil that passes through the screen at the end of 25seconds is then measured. If at least TABLE I Effect of Additives on LowTemperature Properties of Fuel Oil A Additives Used ASTM Recov- PourAmorphous Polymeric ery in Point Hydrocarbon Pour Depressant Flow ofBlend Test "F. None 0.01 wt. EVAOL 1 35 None 0.01 wt. APS l 30 0.5 wt.None -15 0.5 wt. 0.01 wt. EVAOL 1 l5 0.5 wt. 0.01 wt. APS 95 30 EVAOLEthylene-Vinyl Acetate-Olefin Copolymer APS Alkylated Polystyrene TABLEII Effect of Additives on Low Temperature Properties of Fuel Oil BAdditives Used A ASTM Recov- Pour Amorphous Polymeric ery PointHydrocarbon Pour Depressant in Flow of Blend Test F. None 0.02 wt. EVA 350 None 0.02 wt. APS 5 30 None 0.03 wt. FUV 1 25. 0.4 wt. None l0 0.4wt. 0.02 wt. EVA. 100 20 0.4 wt. 0.02 wt. APS 100 -40 0.4 wt. 0.03 wt.FUVA 100 25.

EVA Ethylene-Vinyl Acetate'Copolymer APS Alkylated Polystyrene FUVAFumarate Ester Vinyl Acetate Copolymer The added hydrocarbon fractionwas an amorphous material having a melting point of 1 11F. that wasobtained by propane precipitation from the deasphalted residuum of aTexas coastal crude oil. This hydrocarbon fraction was found by massspectographic analysis and gas chromatography to contain no more than atrace of normal paraffin hydrocarbons and consisted of 5 wt. ofisoparaffins, 22 wt. of aromatic hydrocarbons and 73 wt. ofcycloparaffins. The numer average molecular weight of this material wasabout 775 as determined by osmometry. The distillation characteristicsof this solid hydrocarbon fraction were as follows:

Distillation Vapor Temp. (ASTM Vapor Temp. Converted to D-1l60) at 5 mmHg Atmospheric Pressure Initial BP 442F. 754 5% 590 926 10% 636 978 20%686 1034 24% 689 1037 Only 24% would distill over There were 75%bottoms, and l% loss The ethylene, vinyl acetate, alpha-olefin copolymer(EVAOL) was prepared by the copolymerization of a mixture of about 10wt. of alpha-olefins in the C C range, about 25 percent of vinyl'acetateand about 65 percent of ethylene. The copolymer had a number averagemolecular weight of about 3,450 as determined by osmometry.

The alkylated polystyrene (APS) was prepared by the methods outlined inU.S. Pat. No. 2,756,265, e.g. Example 8, using as the alkylatingmaterial a mixture of C to C olefins averaging about C The alkylatedpolystyrene had an intrinsic viscosity of about 0.25, corresponding to anumber average molecular weight of about 1,200.

The copolymer of fumarate esters and vinyl acetate (FUVA) was preparedby polymerizing 0.4 mole of vinyl acetate with 0.16 mole of mixeddialkyl fumarates in which the alcohols used in making the fumarateesters were mixed C C linear primary alcohols. The polymerization wasconducted in heptane solution at 85 C. using benzoyl peroxide catalyst.The copolymer was recovered by flash evaporation of the volatilecomponents and the copolymer was found to have a number averagemolecular weight of about 15,400 as determined by vapor phase osmometry.

The copolymer of ethylene and vinyl acetate (EVA) had a mole ratio ofethylene to vinyl acetate of about 4.2 and an average molecular weightas determined by vapor phase osmometry of about 1,740. Polymerizationwas conducted at a temperature of about 180 F. in the presence ofdi-lauroyl peroxide catalyst.

It will be seen from the test data that although all of the polymericmaterials were effective pour point depressants in each of the fueloils, only the fumaratevinyl acetate copolymer and the alkylatedpolystyrene were as effective pour point depressants in the presence ofthe amorphous hydrocarbon flow improver as in its absence, and neitherone interfered with the low temperature flow improving properties of theadded amorphous hydrocarbon material. Both of these materials fit thedefinition of suitable additives for the present invention. The ethylenevinyl acetate copolymer and the ethylene, vinyl acetate, alpha-olefinterpolymer are pour point depressants that are outside of the scope ofthe present invention.

What is claimed is:

1. A wax-containing petroleum distillate fuel having a boiling rangewithin the limits of about 250 F. and 700 F. which has been improvedwith respect to its low temperature flow properties by adding thereto:

from about 0.1 to about 3 weight percent of a flowimproving, amorphous,normally solid essentially saturated hydrocarbon fraction that issubstantially free of normal paraffin hydrocarbons, said fraction havinga number average molecular weight of from about 600 to about 3000, andhaving been obtained from a residual petroleum oil,

and from about 0.005 to 1 wt. of a polymeric pour point depressantadditive of number average molecular weight within the range of about800 and about 50,000, the polymeric additive having a monomerrelationship represented by the formula: (A) (3),, wherein x is aninteger 0 to 3, B is an alpha, beta unsaturated ester of from 4 to 8total carbon atoms, and A is an unsaturated compound of the generalizedformula:

wherein R and R are hydrogen or methyl, R is a C to C alkyl groupconnected to the designated unsaturated carbon atom through an aromatichydrocarbon group or through an ester group, and R is hydrogen, acarboxyl group, or the same as R with the proviso that x does not exceed2 when R is hydrogen or a carboxyl group.

2. Fuel composition as defined by claim 1 wherein there are present fromabout 0.2 to 1 wt. of said substantiallynormal-paraffin-hydrocarbon-free fraction and from about 0.01 to 0.1 wt.of said polymeric pour point depressant.

3. Fuel composition as defined by claim 1 wherein the proportion of saidsubstantially normal-paraffinhydrocarbon-free fraction to said polymericpour point depressant is within the range of 50:1 to 1:1, parts byweight.

4. Fuel composition as defined by claim 1 wherein said polymeric pourpoint depressant is an alkylated polystyrene. A

5. Fuel composition as defined by claim 1 wherein.

said polymeric pour point depressant is a copolymer of alkyl fumaratesand vinyl acetate.

2. Fuel composition as defined by claim 1 wherein there are present fromabout 0.2 to 1 wt. % of said substantiallynormal-paraffin-hydrocarbon-free fraction and from about 0.01 to 0.1 wt.% of said polymeric pour point depressant.
 3. Fuel composition asdefined by claim 1 wherein the proportion of said substantiallynormal-paraffin-hydrocarbon-free fraction to said polymeric pour pointdepressant is within the range of 50:1 to 1:1, parts by weight.
 4. Fuelcomposition as defined by claim 1 wherein said polymeric pour pointdepressant is an alkylated polystyrene.
 5. Fuel composition as definedby claim 1 wherein said polymeric pour point depressant is a copolymerof alkyl fumarates and vinyl acetate.